The present paper reports findings of two experiments on filtered sounds of the Standard German vowels /i-y-e-ø-ɛ-a-o-u/ produced by a female speaker at two fundamental frequencies fo = 220 Hz and 659 Hz and a male speaker at fo = 131 Hz and 523 Hz. High-pitched sounds were included in order to account for a possible impact of the fo level on the perception of filtered vowel sounds. In the first experiment, the frequency region of the first formant of the sounds was highpass filtered, and in the second experiment, the frequency region of the second formant of the sounds was lowpass filtered. Vowel recognition of all sounds was investigated in a listening test. Results revealed shifts in the perceived vowel quality which varied across (i) vowel categories, (ii) fo, and (iii) filter cutoff frequencies. Details of the filter parameters and of the perceived vowel quality shifts are given in the paper and implications for the relationship between acoustic cues and vowel recognition are discussed.